Error-correcting system



P. G. NEuMANN ERRoRcoRRBcTNG sYSTEM 5 SheetSSheet 2 Fi1ed May 12, 1961Au 28, 1962 P. G. NEUMANN ERROR-coRREcTING SYSTM 5 SheetsSheet 3 Fi1edMay 12 1961 Au 28, 1962 P. G. NEuMANN 3,o51,784

ERRoRcoRREcTNG SYSTEM Fi1ed May 12, 1961 5 SheetSsheet 4 Au 28, 1962 P.G. NEUMANN 3,051,784

RRoRcoRRBcTNG SYsTEM Fi1ed May 12, 1961 5 SheetsSheet 5 This inventionfelates to digita1 infofnlatioI1 tfansIniS- sion sySten1S, and n1ofepafticulafly to the auton1atic coffection of eff()TS in SUch SySten1s.

The pfoblen1 of coffectly tfaflsInitting binafy Signals ovef a noisychannel iS a SigT1ificaflt one whoSe solution haS been actively Songht.son1e ilII1stfafive SitllationS iI1 vvhich thiS pfobleIn afiSeS afe=vVhen telephone lifleS Subiect to effof impulSes afe being uSed totfanSmit d'ata iI1 biflafy fofn1; vhen an ilflpeffect medinn1 such asnlagnetic ta e of a photogfaphic eff1111sion iS USed to stofe binafydata; of vhen opefatioI1S on binafy signals afe being canied o11t bynleanS of cifcI1its conStfucted of de viceS S11ch as fe1ayS diodes, oftfa11SiStofS, vvhich have a pfobability of effof.

By the 11Se of fedUndancy it is poSSible to encode a fneSSage foftfa11Sn^1ission in such a vvay that a decodef iS able to extfact theofigillal iI1fofI1ation content ffofn the fedundant n1eSSage despife thefact that the nlessage nlay have been fT111tilated dufingtfanSffliSSion.

vAn obiect of the pfeSent i1vention is the in1pfovefflent of digitalinfofnlation tfansn1iSsion sySten1S.

Mofe SpeciCa1fy, an obiect of this iI1vention is a fe dnndant digitaliffofInation ffansn1ission SySten1 vvhoSe effof-coffecting capabilitieSextend to ff1I11ti1)1e effofS.

Anothef obiect of the pfeSent invention iS a selfcoffecting fedUndanttfaf1SIfliSSion sySteIn WhoSe ovefall ofganization iS chafactefized byextfen1e Sin1plicity of de These and othef obiects of the pfesentif1vention afe fealized in an illIlStfative SySteff1 en1bodifIlentthefeof Which con1pfiSeS a Soufce that Supplies infoffflation vofdS toan encodef, the encodef convefting the infoffflation vofdS into o1odi0edwofdS containing s11fficient fe dundancy fo pefmit the wofds to beslightly mutnated by a floiSy channel and still be coffectly inteIpfetedby a decodef. channe1 to the decodef, Which feconStfnctS the ofiginaliI1foffflation vVofds if the InI1tilation has flot been eX- ceSSive Inthe ill11Stfative SySten^l the fedundant binafy code v/ofds to betfanSfnifted ffom the encodef to the decodef con1pfiSe the code vvofdSand the conpleffentS thefeof of a cyclic peffnutation Set. Fof thespecific eXanlple of a code Set inclnding N n-digit wofds, it iSobsefved that each vvofd of the set inc1UdeS a uniqUe y(git sub Setidentifief. T1eSe N SubSets afe the infoffflation WofdS to be encodedand decoded. The I11i11if111n1 nUn1bef of digit positionS in WhichvVofdS of the set diffef iS zZ- In othef wofds, the minimnn1 distancebeheen code wofdS iS d.

If1 the illLIStfative encodef a ydigit infoffflation Wofd iSSllcceSSiZely conlpafed vith the SubSets of one-half of the dfgit WofdSof the code Set, theSe Wofds of the code Set being SeqlleI1tiallygenefated by a sI1itable cifcl1 The Inodified wofdS afe Sent via thenoiSy v gating the invefse of the genefated code vvofd to flle vvofds, aSecond Sigllal is pfovided to gate the invefSe of conlplefnent of theone code vvofd to the channeL The illuStfative decodef feceiveS afedundant digit Wofd ffom the channel and is capable of abStfactingthefeffon1 the ofigiI1al infofIation vvofd even if the fe dnnat vvofdWas fnUtilated dufing tfansff iSSion in m1 adiacent of nonadiacent digitpoSitions.

In the decodef the feceived fednndant vofd is sI1c cessively compafedWith oneha1f of the digit Wofds of the code set, these Wofds of the codeset being Se quentially genefated by anothef cifcUlating Stofage de vicehaving Stofed thefein only one of the vvofdS of the code set. T11efesultS of the co1pafiSon opefation afe coupled to t o cifc11ifs, one ofvvhich pfovides aJ1 oIItpuf ASSI1ffle that an Unn1utilated vvofd isfeceived by tho decodef. Compafison of the unfnntilated vvofd vvith ofthe N/Z vvofdS genefated by the cifculating Sfofage device tfiggefSneithef one of the above-1entioned cff cnits. Howevef, Con1pa iSon ofthe UnIflI1tilated Wof(f with the N/Z genefated vofd necesSafilytfiggefS one of the ()thef of the tvvo cifcllitS depending fespectivelyUpon vhethef the feceived W()fd iS identical t() of the eXact invefse ofthe genefafed Wofd, In tufn, thiS tfig gefing action caUSeS eithef theinfofn1ation SI1bSet of the identical genefated wofd of the invefSe ofthe infofn1a tioI1 SubSet of the genefated vvofd to be gated oI1t of thedecodef Sifnilafly, if the digit fedndaJt Wofd becon1eS nlutifateddnfing tfanSIfliSSion in 71 digit poSitionS, only the Conf )afiSonbetvveen the n1ntilated vvofd and one of the genefated vvofdS Will,becaUse of the diStance pfopefties of the code set, tfiggef one of theothef of the noted cifooits to pfovide a gatig Signal. In the caSe of a1111tilated fedundant vVofd, fhe coffect ilfoffflation wofd isfecogoized by the decodef vvithout conSidefatiofI of exaotly vvhichdigits of the feceived vvofd Wefe in effof.

It iS a featUfe of the pfeSent inveI1tio11 that a Self-coffectingdigital infofn1ation tfansfniSSioI1 SySteIf1 i11c111do an encodef vvhichcoInpfiSes a fifSf cifcuit fof genefat ing a plIfality of iI1fofnlationvvofds, a second cifcuif fof seqnentially genefating one-half of thevvofdS of a,

iS identical to one of the sLlbSets and a Second gafing s1g11a1 if theif1f()fIIlation wofd iS the exact invefSe of of1e of the SUbsetS, and afoI1fth cifcuit feSponSive fo the fifSf gatfng Signa1 fof gating thegenefated code vvofd to a channel and fesponsive to tho Second gatingsignal fo1 channeL t is anothef featufe of this inve11tion thaf aSelfcof fecting digitl infofIIlation tfanSnission sySten1 include adecodef oonnected to the noisy chafnel fof feceiving fhefeffoo1 codevofd vvhioh Inay have been n111filated,

fhe decodef i11cluding a fifSt cifoIliJt fof Sequentially genef atingone]a1f of the wofdS of the code set to Vhich tho feceived code vvofdbelongS, o. Second cifcnit feSponSive to a fecelved code Wofd and to theontput oode wofd of the fifst cifcuit fof SucceSSively cofnpafing thefeceived SifnTly, the 1 Signal oUtput of the ate 318, Which signaL it iSfecalled, feSUlts ffon1 the feceipt by the de codef of a n111ti1ated of11nfnIltilated coontefpaft of the exact con1plenent of one of the vvofdSo thfongh o iS paSSed thfough the OR oifcUit 336 to gate thfongh the ANDcifcUits 361 thfongh 365 the digitS appeafing in poSitionS thfoI1gh 4 ofthe output code vvofd Stofed at that time in the cifcUlating fegistef340. This 1" si nal iS also a 1ied as an in ut si nal to each of theEXCLUSIVE-oR circuits 371 throu h 375, thereb causiI1g the Signals Whichappeaf on the infofII1at1on output 1eadS 381 thfongh 385 to be thefeSpective cofnpleInents of the outpUtS of the AND cifcuits 361 thfoogh365.

Thus, Whethef the fedUndant infoffnation Wofd fe ceived by the decodefwas Unmuolated of whethef the Wofd contained aS Inany as 3 digit effofS,the coffect SobSet thefeof is gated ont of the fegistef 340. It iSSigni11cant to note that th1s is acomp11Shed Without the decodefactua1ly Speci1ically fecognizing Whioh, if any, of the feceived digitsWefe in effof,

The cifoulating fegiSfef 340 may take any one of Sevefa1 fofn1S.Il111Stfat1ve1y it noay be of the genefal fofIT of the fegistefdeScfibed above and shown in 1G. 4. Howevef, it is to be undefstood thatany Suitab1e cifcl11atiflg Stofage affangen1ent, vvhethef it inc1ude apunched papef tape, a photogfaphic enTulSion, a peffofated disc, an1agnefic tape, et cetefa fnay be emp1oyed as the fegistef 340 (of thefegiStef 130).

The 0 L Z 3-oUtof15 gate 316 that is i11clllded in the FIG. 7 decodefmay, fof exaIn le, be of the fofn1 Shown 111 detai1 in FIG. 3. The gate316 of 1G 8 includeS a tfanSfoffnef asseInbly con1pIiSing inpUt Windings801 t11foI1gh 815 and an ontput vvinding 816- (Zonnected to the out ntwindin 816 of the transforn1er assen1bl is a thfeShold detectof 8Z0i1111stfativoly, a diode of a tfan- Sistof, Which iS adiUSted to pfovidea 1 signa1 on the oUtpnt 1ead 317 thefeof only if dfiving 1 Signa1S afea olied to 0, 1, Z of 3 of tho inpnt WindingS of the aSSen1bly.

Additiona11y, 3. Specifio i11UStfative embodiment of the 1Z 13, 1415-oUt-of-15 gate 318 of the FIG. 7 decodef iS Shown i11 FIG. 9, Te gate318 of FIG. 9 includes a tfaSfofmef aSSembly con1pfising 15 inputWindings 901 thfough 315 and an o11tput Willding 916. Connected to theontput vvinding 316 iS a thfeShold detectof 930 Vvhich iS adinsted topfovide a 1 Signa1 of the oUtput lead 310 thefeof on1y if dfiviog 1Signa1S afe applied to 12, 13, 14 of 15 of the input windingS of theaSSen1b1y.

T11e othef con1ponent cifcL1its o11t of vvhich the Specic decodef Shownin F1G. 7 iS fofn1ed afe known and com pletely conventionaL and afe,accofdingly, not Shovvn in defai1 in the dfaWing.

Both the encoding and decoding opefationS descfibed above Inay becaffied oUt on eithef a Synchfonous of an aSynchfono11S basiS. FofeXaInple if fedundant wofdS Which afe feceived ffofn the channe1 by thedecodef afe equa11y spaced in tiITle, it is neceSSafy that the tinleintefval fequifed fof (1) a vvofd to be fead into the decodil1gcifcuitfy, (Z) cyc11ng of the fegistef 340 thfough the 15 Wofds ZthfoUgh o and (3) a v/ofd to be fead out of the decoding cifcllitf andapplied to the infofn1ation output leads 381 thfongh 385, be 1eSS thanthe tifne intefva1 betWeen al'fiva1S of fedondant WofdS at the decodef.

on the othef hand if the affiva1S of fedundant infof n1ation Wofds atthe decodef afe Suitably bUefed, fof exaInple, feceived on a stofage tae (not Shown and then de1ivefed to the fegiSfef 320 Upon fequest, thetin1e fe qI1ifed fof the decoding opofation may in effect be cut inha1f. SpecicaHy, thiS may be accoInp1iShed by app1ying the 1 signaloUtpnt of the gateS 316 and 318 to the bIlffef stofage tape to conffo1the tfanSfef of a wofd ffom the tape to the fegiStef 320. In this caSe,the cycling action of the fegiStef 340 can go on Without inteffuptiof1ffom vhatevef point it left off dUfing the decoding of 10 the I)fevioUSfedundant infofnlation vvofd. ssun1ing that fedundant infofInationvvofds afe applied fo the decodef in a fandofn faShion, only 7z codevvofds, fathef tha11 15, vvoUld on the avofage have to be genefated bythe cifculating fegiStef 340 in ofdef to decode a feceived infofmationWofd.

7S indicated above, the encodef n1ay a1so be opefated on an aSynchfonousbaSis, if1 vhich caSe the 1 Signa1 output of the gateS 150 and 155 iSuSed to tfiggef the soufce to cause feadin of an ofiginal infofnlationWofd to the fegistef 110. 1n this Inode of opefatiof1 the avefagenIlxnbef of vvofds fequifed to be genefated by the fegiStef dufing thoencoding of an infofn1ation vVofd WoU1d be on1y 7 vvofds.

The effof coffection Systefn deScfibed hefein may be Ifod1ed to pefnlitencoding of the infofnlation Wofds 00000 and 11111, thefeby to pfovidetheif feSpective code WofdS A and A (F1(}. 1) fof tfaI1SffliSSion to thedecodef. This may bo accompHShed, fof examp1e, by modifying theCifcl11ating fegiStef 130 so t11at dufing soffle poftion of its Cycle ofopefation it pfovides af1 al1-Zefo oUtput vVofd. 1n that caSe thedefection by the 0-oL1tof5 cifcuit of the infoffnation Wofd 00000ca11Ses the code wofd /1 to be gated out of t11e fegiStef 130, Whi1e thedetection by the 5o11tof-5 cifc11it of fhe infofII1ation Wofd 11111causos the code vVofd 1 to be gated ont of the fegiStef 130Altefnatively, the fegistef 130 need not be n1odi Hed and detectioncifouitS vhich afe uniquely fesponSive to the infofmation wofds 00000and 11111 may be pfo vided to supply contfo1 SignalS to inhibit theoutput of the fegistef 130 of to cause the feg1Stef 130 to enfifa11-()11e Sequence,

Sin1ilafly, the decodef and Speci5cany the cifcUlating fogiStef 340thefeof Inay be Inodi1ied to pfovide fof the decoding of the fedundantinfoffnation WofdS A and A If thefe afe 0, L Z of 3 -1,S in the feceivedfedundant wofd, thon the a11-Zefo code vofd A vvas tfanSn1ifted; Whileif thefe afe 12, 13, 14 of 15 13 in the feceived Wofd, then the a11-onecode vvofd A v7as tfansInitted. Thefefofe, if the fegiStef 340 isInodi11ed so that dufing Sonle poftion of its cycle of opefatioI1 itpfovideS an allZefo oUtpI1t wofd, of if feadont ffoIn the fegistef 340is b1ocked fof a poftion of itS cycle of opefation, the gates 316 and318 of the decodef shown in FTG. 7 may be USed difect1y to pfovide theneceSSafy gating and conplenfentation signalS. need not be IT1odifiedand detection oifcuitS vvhich afe Unique1y fesponsive to the pfesence ofthe code vvofds /1 and 1 1 fnay be pfovided.

The pl-inciples of the pfeSent invention eXtend to the caSo ifl Which apafity check digit is added fo each of the code wofdS fepfesented inFIG. 1 to make the nUmbef of rS in each code Wofd even (of odd). T11efeSUlting SyStem en1bodinoent of Such a oode iS then capab1e not only ofcoffecfing 1 adjacent of nonadiacent digit effofs in each fedundantinfofnlation wofd but alSo of detocting an afbitfafy m-di'git effofthefein.

To n1odify the encodef Shovvn in FI(}. 3 fof the case in vhich eachfedundant infoffnation vvofd is to inc1nde an even paf1fy check digit,it iS on1y neceSSafy to add to the encodef anothef lead 106 vVhichdifectly connectS the Out ut of the 3-out-of-5 gate 155 to thetfaf1SIniSSiofl channeL T1iS iS So becanSe each of the code Wofds othfough o a1feady containS an even numbef of 1 s, whefeas each of thecode vvofdS thfogh 5 contains an odd nun1bef of rs and vvoUld,thefefofe, fequife the SI11fiXing of anothef 1 digit thefeto.ad(1itiona1 1ead 136 iS ShoWn in FIC. 3 iI1 dotted lines.

To modify the decodef Shown if1 FIG. 7 so that it can feceive a 16-digitfednndant if1foffflation vvofd vvhich includes an even pafity checkdigit, it iS neceSSafy to add an additiona1biStable cifcUit 337 to thefegiStef 320 to feceive t11e 16th digit ffofn the tfanSn1iSSioo channeLas A1tefnatively, the l`egistef 340- Note that the 13 WheTe y1og 8, anda y-stage iofofnnation Wofd TegiSte1 reSponsive fo the ol1f )I1t of SaidsoI1rce.

13. A con1bination aS in clain1 12 vvherein Said second n1eanS iI1cludesa cifcnlating TegiSter oo1priSing 71 bi Stable eleInentS,

14. A oon1bination as in c1aim 13 vvheTein said neanS TeSponSive to theoutput words of Said TSt and seoond nleanS inc1ndeS y n1odulo Z addercircuitS Tespectively TosponSive to the StateS of the y StageS of saidinfonnation WoTd Tegistel and to the StateS of y of the biStableelen1entS of Said ciTculafing TegiSter.

15. A con1binafion aS in olaiIn 14 vheein Said Inea11s TeSponSive to theoutput voTdS of Said fSt and second Ineans further includes a ootofgateTeSponSive to the outpI1tS of Said y n1odnlo Z adder ci1ol1its fo1pToviding said 1iTSt gating signaL and a y-ont-of-y gate TeSponSive tothe outpnts of Said y Inodulo Z addeT ciTcuitS foT providing said Secondgating signal.

16. A con1bination aS in claim 1S vvheTein said nleanS TeSponsive toSaid TSt and second gating SignalS includeS AND CircI1its TespectivelyTesponSive to the stateS of the biStable e1ements of Said ciTcu1atingTegiSter, and n1odu1o Z adder oifcuitS TeSpectively TesponSive to theo11tut si nals of Said H AND circuitS, each of said modnlo Z addercircuitS being aISo TeSponsive to Said 1ifSt and second gating Signals.

17. Incon1bination in a decodeT that is connected fo a noiSytfansIniSSion channe1 for Teceiving thereffom an H di it code word whichnla be InI1tilated in m 1 di it oSitionS, Whefe 7- iS any positiveintegeT greator than one, ad 41, Ineans fof Sequentiany goneratingone-half of the woTds of a code Set of Whioh Said Teceived vvord is aTnen1bef, nleanS feSponSive to a Teceived vvord and fo the outpUt v7ordSof said geneTating nleans fol succesSively compafing said Teceived wofdvifh Said ontput WoTdS and for providing a fiTSt gatiI1g sigllal if SaidTeceived vvoTd aI1d one of Said o11fput vvoTds differ in Z1 digit poSitionS and for pfovding a second gating sigTlal if Said Teceived Vvordand one of said output vvords diffe1 in (H1) digit }ostioI1S, and-IneaI1S TeSponsive to Said fSt gating Signal foT gating out of SaiddecodeT the uniqne SubSet of the onbput word WhoSe con1paTiSon reSulfedi11 Said differellce of 1 digitS aJ1d TeS onSive to said Sec ond gatingSignal for gating out of said deooder the in veTSe of the nniqlle SbSefof the ontput vvoTd hose con1- pariSon resulted in Said difference of(m1) digiS.

18- A con1bi11ation aS i1clain1 17 WheTein said geneat ing meansincludoS a ci1cU1afing TegiSfer conlpTiSing bi Stable eleInentS.

19- A cofnbination as i1 c1aiI11 18 vvherein said Tneans reSponSive fo aTeceived vvord and to fhe oIltput WvofdS of said goneTating meansincludeS n1odulo Z addef ciTcl1its TeS ective1y TeSponsive to the binafyvalueS of the digitS of a Teceived wofd and to the StateS of thebistable ele- InentS of said ciTculating Tegister 20. A coInbination asin clain1 19 WheTein Said IT1eans feSponSive to a Teceived word and tothe oUtpUt woTds of said geneTating IneanS fI1Tther includeS a (0, 1, 27z1)-o11tof gate Tespoosive to the outputS of Said 1 TIlodI11o Z addefcirc11its for providing Said 1iTSt gating Si nal and an m1 Z out-ofgateTeSponSive to the outpntS of said Inodulo Z adde1 circuitS fo1 providingSaid Second gating signaL 21. A coInbination aS in claim 20 Wherein saidmeans TeS )onSive to Said irSt and second gating Signals inclI1des y ANDoifctlitS Tespectively Tesponsive to the States of y of the biStableelementS of Said ciTcnlating TegiSter, Whefo y log 8 and y n1odulo Zadder oifcnitS Tespectively TesponSive to the output signals of said yAND circuitS, each of said y n1odu10 2 adder ciTc11itS being a1So TeSponsive to said 1i1St and second gating SignaIS,

No TefefenceS cited.

